HR: 11:10h
AN: GC52A-06    [Abstracts]
TI: A Fully Coupled GCM Study of a "Geoengineered World"
AU: * Lunt, D J
EM: d.j.lunt@bristol.ac.uk
AF: University of Bristol, School of Geographical Sciences University of Bristol University Road, Bristol, BS8 1SS, United Kingdom
AU: Ridgwell, A
EM: andy@seao2.org
AF: University of Bristol, School of Geographical Sciences University of Bristol University Road, Bristol, BS8 1SS, United Kingdom
AU: Valdes, P J
EM: p.j.valdes@bristol.ac.uk
AF: University of Bristol, School of Geographical Sciences University of Bristol University Road, Bristol, BS8 1SS, United Kingdom
AB: Several schemes have been proposed with the explicit aim of modifying the future climate of the planet as a mitigation strategy in a response to anthropogenic global warming. A selection of these, including the placing of mirrors at the Lagrange point between the Earth and the Sun, and the injection of aerosols into the stratosphere, have at their heart the goal of effectively reducing the incoming solar radiation near the top of the atmosphere, to "balance" increased surface warming due to increased greenhouse gas concentrations. However, it is likely that an exact balance of the radiative forcing would be very difficult to obtain, due to differing spatial characteristics of the solar forcing applied (greatest at the equator and least at the poles) and that of long wave absorption (more equal over all latitudes), as well as differing temporal characteristics of the radiative forcings. In this study, we model the different climate expected in a "Geoengineered World", compared to the "Preindustrial World", if both have the same global annual mean surface temperature. We use the UK Met Office GCM, HadCM3L, and carry out 5 simulations: Pre-industrial, Doubled CO₂, Quadrupled CO₂, and 2 simulations in which the increased CO₂ is balanced in the global annual mean by a reduction in incoming solar radiation. The "strength" of mirror/aerosol required is calculated using an iterative procedure, until balance is obtained. Our results indicate significant differences between the Geoengineered World and the Preindustrial World, despite near identical global annual mean surface temperatures. In particular, we obtain relatively large differences in surface temperature over mid-latitude continental regions, in particular North America, and significant changes in upwelling on the West African tropical coast. The drying of the American Mid-West, and impacts on Africa fisheries, are likely to have significant consequences for global and local food production.
DE: 1626 Global climate models (3337, 4928)
DE: 1637 Regional climate change
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting